1. Field of the Invention
The present invention relates to an inflator socket pin collar which serves as the electrical connection between an electroexplosive device or initiator and a automobile passenger restraint electrical system, and more particularly, to a collar which supports the electroexplosive device within a gas generator, and which includes a metal oxide varistor for electro-static protection of the electroexplosive device.
2. Description of the Related Art
It is known in the prior art to employ an inflatable occupant restraint system for protecting a passenger of an automobile. Such restraint systems encompass a reaction canister which houses a gas generator or inflator, and an air bag in an uninflated condition. In response to a collision, the gas generator generates gas to inflate and expand the air bag to protect the vehicle occupant.
Inflators for automobile passive restraint systems or other devices require a pyrotechnic initiator or electroexplosive device (EED) to operate the inflator. For actuating the gas generator or inflator an electroexplosive device starts the material of the gas generator burning. The inflator initiator is connected to a crash sensor that is positioned adjacent the initiator or at a remote location in the vehicle.
In operation, the crash sensor sends an electrical signal to the initiator or squib. The initiator fires into the ignitor chamber and ruptures a container, which holds an ignitor material, commonly a mixture of boron and potassium nitrate. The initiator consists of a pair of spaced parallel electrical pins joined at one end by a bridge wire which is embedded within pyrotechnic material. The pyrotechnic material bums with a very hot flame and ignites solid fuel gas generant pellets contained in the combustion chamber. The pellets release a nitrogen gas, which travels through the diffuser chamber and into the protective air bag for protecting occupants of the vehicle.
A common characteristic of electroexplosive devices (EED's) is that the bridge wire is susceptible to inadvertent radiant energy from outside electrostatic charges. This radiant energy, which may be of an electromagnetic or radio frequency origin, can inadvertently initiate the EED. Protection against such radiant energy will herein be referred to as EMI/RFI protection.
One prior art solution to overcome this hazard involves the use of ferrite beads disposed directly within a chamber of the initiator. The ferrite beads absorb the extraneous energy preventing the energy from reaching the bridge wire. See U.S. Pat. No. 4,306,499 to Holmes, which is assigned to the assignee of the present invention.
A problem with the electroexplosive device of Holmes is that incorporation of the EMI/RFI protection directly within the EED increases both the size of the device, as well as, manufacturing costs and time. Moreover, the manufacturer of the gas generator is limited to a specific EED design.
Another solution is a universal squib connector which encompasses a ferrite bead which surrounds the electrical terminal of the EED. See U.S. Pat. Nos. 5,200,574 and 5,241,910 to Cunningham et al., assigned to the assignee of the present invention. Cunningham et al. discloses universal connectors encompassing EMI/RFI protection, which are permanently secured within the gas generator. The ferrite bead, electrically, is essentially an inductor which impedes the instantaneous change in current flow.
Another problem with known inflator assemblies is that the EED is crimped into the inflator base. This crimping process often damages the initiator if done improperly.
The use of a metal oxide varistor (MOV) to absorb electrostatic energy in an electroexplosive device has recently been explored. See, V. Menichelli, A Varistor Technique to Reduce the Hazards of Electrostatics to Electroexplosive Devices, (1974).
Typically, metal oxide varistors are used in surge suppression devices, such as computers. However, the prior art has not explored the use of a MOV in an electroexplosive device used as an initiator in an air bag gas generator.